Is a Megabit the Same As a Megabyte?

Whether it’s data storage or device performance, knowing what specs to look at, and understanding their values is crucial to picking the best hard drive or memory unit. There’s a lot to know and evaluate in order to figure out how good a computer device really is, but the basics, like knowing the difference between bits and bytes, are the most important for not making huge mistakes over marketing tricks.

Since a lot of devices use megabytes and megabits to describe their specifications, it’s a good starting point for explaining these basic principles.

What Is a “Mega-“?

Before we go into the differences between bits and bytes, it’s necessary to understand the prefixes for huge amounts of data units. In all other standards and measurements (voltages, weight etc.) the prefix “kilo” means 1’000 (for example, a kilogram represents 1’000 grams), “mega” means 1’000’000, “giga” represents a billion units and so on. However, in computing technologies, each new prefix isn’t 1’000 times larger than the last one, but rather 1024 times larger, meaning that one kilobit, for example, is 1024 bits, and, in turn, 1 megabit = 1024 kilobits.

Byte prefix

Value

Kilobyte, kB

1024 bytes

1'024 (210) bytes

Megabyte, MB

1024 kilobytes

1'048'576 (220) bytes

Gigabyte, GB

1024 megabytes

1'073'741'824 (230) bytes

Terabyte, TB

1024 gigabytes

1'099'511'627'776 (240) bytes

Petabyte, PB

1024 terabytes

1'125'899'906'842'624 (250) bytes

Exabyte, EB

1024 petabytes

1'152'921'504'606'846'976 (260) bytes

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But why use such an off-beat number? It’s because computers work with binary numbers, so computer engineers decided to implement a base 2 number for each new multitude of data, so they chose the closest one to a thousand – 1024 (210). This can cause up to a 10% difference in advertised and actual hard drive sizes, for example, so make sure that the manufacturer shows their specs in the same prefix system as your PC to be sure of the real value.

Bits and Bytes

Now onto the main course – what are bits and bytes and what makes them different? Both are units that represent an amount of data:

Bit – represents one data point, which in computing will be either one or zero. This explains why the previously mentioned binary counting system is used in computing since addressing two states per data “slot” with 10 numbers is unnecessary. You may have seen pictures featuring tons of ones and zeroes in order to represent data – each one and zero in that picture is a bit that has a certain state and the overall amount of these ones and zeroes, in turn, can be addressed with kilobits, megabits, and gigabits, depending on their amount.

Byte – the smallest group of bits a computer can actually use as tangible information. In almost all modern day electronics, 1 byte = 8 bits because all modern computing architectures are able to use each string of 8 bits to encode one basic symbol, for example, 01001000 is translated as “H“.

Bytes are used more often instead of bits because they represent an actually usable amount of information, rather than one state. As an analogy, measuring data in bits is kind of like “car” being addressed as “the wheel-engine-chassis device” – you could do it, but there’s no practical point in splitting it into smaller parts. Therefore memory unit processing power, storage device capacity, device data transfer speeds and many other values are represented in bytes.

On the other hand, bits are used mostly in just one field – wireless and wired data interface speeds. This includes universal interfaces, like USB and PCIe, as well as ones for more specific uses, like SATA. The data transfer speeds of these connections are measured in bits per second (bps, or b/s), as opposed to just bits. Wireless and wired internet connection speeds are also measured in bits per second. Although bits are mainly used just in this context, it’s a pretty big context, involving, to some extent, pretty much any device that isn’t integrated into a processor.

The fact that device speeds are measured mostly in bytes per second, while the connections between them are rated in bits per second, forces consumers to do a bit of math every now and then. This is to make sure that a device doesn’t get bottlenecked, i.e. that a super-fast device isn’t connected to a port too slow to handle the device. For example, you could connect a 500 MB/s solid-state drive to a USB 2.0 port (480 Mbps), at which point you’ll get as much speed as the port can handle, regardless of the huge speeds that the drive itself can dish out. To help you out, we did the math for you on the most used PC interfaces, so that you know what to compare device performance with. Note that some interfaces actually use other forms of encoding, like SATA’s 10-bit encoding, meaning that 1 byte in this specific case will be 10 bits.

Interface

Data transfer speeeds

Bits per second

Bytes per second

USB 2.0

480 Mbps

60 MB/s

SATA Revision 2.0

3 Gbps

300 MB/s

PCIe 2.0 x1 (1 channel)

5 Gbps

500 MB/s

USB 3.0 (3.1 Gen 1)

5 Gbps

625 MB/s

SATA Revision 3.0

6 Gbps

600 MB/s

PCIe 3.0 x1 (1 channel)

7.88 Gbps

985 MB/s

USB 3.1 (3.1 Gen 2)

10 Gbps

1250 MB/s

USB-C

10 Gbps

1250 MB/s

Thunderbolt 2

20 Gbps (total)

2.5 GB/s

Thunderbolt 3

40 Gbps (total)

5 GB/s

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